A digital image begins as an analog signal. Through computer data processing, the image becomes digitized and is sampled multiple times. The critical characteristics of a digital image are spatial resolution, spectral resolution, radiometric resolution, contrast resolution, noise, and dose efficiency. These depends upon satellite orbit configuration and sensor design. Different sensors have different resolutions.
Spectral resolution describes the ability of a sensor to define fine wavelength intervals. The narrowest spectral interval that can be resolved by an instrument. Spectral resolution (spectral capability) also refers to the number of wavebands within the EM spectrum that an optical sensor is taking measurements over.
Radiometric resolution can be defined as the ability of an imaging system to record many levels of brightness. Radiometric resolution refers to the range in brightness levels that can be applied to an individual pixel within an image, determined on a grayscale. E.g., Sentinel-2 sensor MSI is a 12 bit sensor imaging with 4.096 levels.
Spatial resolution of an image corresponds to the size of the minimum area that can be resolved by the sensor.
Temporal resolution, also referred to as the revisit cycle, is defined as the amount of time it takes for a satellite to return to collect data from exactly the same location on the Earth. Imageing of the exact same area at the same viewing angle a second time is temporal resolution.